Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 396, Issue -, Pages 78-87Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2014.04.015
Keywords
Fe-S liquid; velocity; density; equation of state; high pressure; lunar core
Categories
Funding
- National Science Foundation [EAR-0711057, 1214376]
- NSF [EAR-0622171]
- U.S. Department of Energy (DOE) [DE-FG02-94ER14466]
- DOE-NNSA [DE-NA0001974]
- DOE-BES [DE-FG02-99ER45775]
- NSF
- DOE Office of Science, Basic Energy Sciences [DE-ACO2-06CH11357]
- Division Of Earth Sciences
- Directorate For Geosciences [1214376] Funding Source: National Science Foundation
- Grants-in-Aid for Scientific Research [25800292] Funding Source: KAKEN
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Sound velocities of Fe and Fe-S liquids were determined by combining the ultrasonic measurements and synchrotron X-ray techniques under high pressure-temperature conditions from 1 to 8 GPa and 1573 K to 1973 K. Four different liquid compositions were studied including Fe, Fe-10 wt% S, Fe-20 wt% 5, and Fe-27 wt% S. Our data show that the velocity of Fe-rich liquids increases upon compression and decreases with increasing sulfur content, whereas temperature has negligible effect on the velocity of Fe-S liquids. The sound velocity data were combined with ambient-pressure densities to fit the Mumaghan equation of state (EOS). Compared to the lunar seismic model, our velocity data constrain the sulfur content at 4 3 wt%, indicating a significantly denser (6.5 +/- 0.5 g/cm(3)) and hotter (1870(-70)(+100) K) outer core than previously estimated. A new lunar structure model incorporating available geophysical observations points to a smaller core radius. Our model suggests a top-down solidification scenario for the evolution of the lunar core. Such iron snow process may have been an important mechanism for the growth of the inner core. (C) 2014 Elsevier B.V. All rights reserved.
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